Solve for $x$ and $y$ using substitution. ${-5x+y = -9}$ ${y = -3x+7}$
Since $y$ has already been solved for, substitute $-3x+7$ for $y$ in the first equation. ${-5x + }{(-3x+7)}{= -9}$ Simplify and solve for $x$ $-5x-3x + 7 = -9$ $-8x+7 = -9$ $-8x+7{-7} = -9{-7}$ $-8x = -16$ $\dfrac{-8x}{{-8}} = \dfrac{-16}{{-8}}$ ${x = 2}$ Now that you know ${x = 2}$ , plug it back into $\thinspace {y = -3x+7}\thinspace$ to find $y$ ${y = -3}{(2)}{ + 7}$ $y = -6 + 7$ $y = 1$ You can also plug ${x = 2}$ into $\thinspace {-5x+y = -9}\thinspace$ and get the same answer for $y$ : ${-5}{(2)}{ + y = -9}$ ${y = 1}$